<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 群组选择器:提供公共代码,节约代码量. */
        /* div{
            background-color: yellow;
        }
        p{
            background-color: yellow;
        }
        h1{
            background-color: yellow;
        } */
        /* div,p,h1{
            background-color: yellow;
        } */
        div,.boxp,h1{
            background-color: yellow;
        }

    </style>
</head>
<body>
    <div>111111</div>
    <p class="boxp">111111</p>
    <h1>111111</h1>
</body>
</html>